Abstract

We have investigated the correlation between magnetic and structural properties in exchange coupled polycrystalline CoO/Fe thin films. It has been found that an increase in interface roughness increases the exchange bias field as well as the coercivity. The magnetization reversal mechanism is also influenced by the interfacial morphology. Smooth interfaces are characterized by an asymmetric hysteresis loop, which is associated with domain wall motion for the first magnetization reversal after field cooling and spin rotation in all subsequent reversals. This asymmetry diminishes as the interface roughness increases, i.e., all magnetization reversals are dominated by spin rotation. Moreover, we have observed that the blocking temperature decreases with increasing interface roughness. We also report on a logarithmic time dependence of the magnetization which is different for both branches of the hysteresis loop of smooth CoO/Fe bilayers.

Received 03 December 2009Accepted 16 March 2010Published online 02 June 2010

Acknowledgments:

This work was supported by the Fund for Scientific Research-Flanders (FWO) as well as by the Flemish Concerted Action (Grant No. GOA/09/006), the Belgian Interuniversity Attraction Poles research programs (Grant No. IAP P6/42), by the K.U. Leuven BOF (Grant No. CREA/07/005) program and by the Centers of Excellence Programs (INPAC under Grant No. EF/05/005).